曲线拟合在核探测器信号幅度提取中的应用

研究数字化核探测器输出脉冲信号的幅度提取问题。根据闪烁探测器的电路特性，推导了其脉冲信号理想曲线方程。综合利用三和值法、最小二乘法、试探法等方法，设计了该理想曲线拟合算法。由脉冲信号采样点数据，通过曲线拟合，计算出曲线的极大值，该值即为闪烁探测器输出脉冲信号的幅度。正反演数据结果对比表明，采用曲线拟合算法提取闪烁探测器输出脉冲信号幅度，其方案可行，计算结果更准确。相较于数字滤波和数字脉冲成形方法提取核探测器输出脉冲幅度，该算法更简单，对仪器的硬件处理速度要求更低。该方法开辟了核探测器脉冲幅度提取的新途径。     

An Improved Hilbert Curve for Parallel Spatial Data Partitioning

A novel Hilbert-curve is introduced for parallel spatial data partitioning, with consideration of the huge-amount property of spatial information and the variable-length characteristic of vector data i...     

The problem of underpowered rivers

This study has hypothesized that for many rivers the trade-off between flow accumulation and the decrease in slope along channel length means that stream power increases downstream and, moreover, that given the low slope angles in headwater and low-order streams, they would have insufficient stream power to erode let alone transport sediment. The study considered the stream power profile, the particle travel distances and the application of the Hjulström curve based on the velocity profile of nine, large UK catchments. The study showed that:

1. Some rivers never showed a maximum in their longitudinal stream power profile, implying that some rivers never develop a deposition zone before they discharge at the tidal limit.
2. Particle travel distances during a bankfull discharge event showed that for some rivers 91% of the upper main channel would not be cleared of sediment. Furthermore, while some rivers could transport a 2 mm particle their entire length in one bankfull event, for another river it would take 89 such events.
3. The Hjulström curve shows that for three of the study rivers the upper 20 km of the river was not capable of eroding a 2 μm particle.
4. The study has shown that for all rivers studied, erosion is focused downstream and deposition upstream. Many UK rivers have a dead zone where, on time scales of the order of centuries, no erosion or transport occurs and erosion only occurs in the lower courses of the channel where discharge rather than slope dominates – we propose these as underpowered rivers.

© 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd     

GIS中平面面位误差环的解析模型

本文基于随机场理论,导出了随机面元的分布函数和概率密度函数。为了衡量随机面元的位置不确定性,将点位误差椭圆和线位误差带进一步扩展到面位误差环指标。根据推求包括线的原理,导出了多边形面位误差环边界线的解析表达式,并分析了面位误差环的构成机理,证明了误差环边界线为连续闭合曲线的结论。最后通过实例绘制了面位误差环的可视化图形。     

低周反复荷载作用下复合耗能支撑钢筋混凝土框架结构的抗震性能试验研究

本文介绍了三榀钢支撑钢筋混凝土框架结构（包括两榀复合耗能支撑框架、一榀普通支撑框架）在低周反复荷载作用下的试验结果。对复合耗能支撑框架结构在低周反复荷载作用下的工作性能（包括受力性能、破坏形态、滞回曲线、骨架曲线、延性和耗能能力等）进行了探讨,揭示了复合耗能支撑框架结构良好的抗震性能。     

应用地理信息进行无资料地区流域水文模拟研究

无资料或资料缺乏地区的流域径流模拟是水文学研究中的一个重要的课题.提出了应用地理信息系统分析流域的地理信息参数,进行降雨径流模拟的水文模型.该模型中,产流计算采用美国水土保持局(SCS)的径流曲线数法,流域汇流则采用经本文作者改进的三角形单位线.着重阐述了利用地理信息系统,从流域的地理信息中分析和确定模型参数,还简要介绍了该模型在爱尔兰Dodder河上的应用情况.     

Derivation of a curve number and kinematic-wave based flood frequency distribution

Abstract

The physically-based flood frequency models use readily available rainfall data and catchment characteristics to derive the flood frequency distribution. In the present study, a new physically-based flood frequency distribution has been developed. This model uses bivariate exponential distribution for rainfall intensity and duration, and the Soil Conservation Service-Curve Number (SCS-CN) method for deriving the probability density function (pdf) of effective rainfall. The effective rainfall-runoff model is based on kinematic-wave theory. The results of application of this derived model to three Indian basins indicate that the model is a useful alternative for estimating flood flow quantiles at ungauged sites.     

Development of a continuous soil moisture accounting procedure for curve number methodology and its behaviour with different evapotranspiration methods

The curve number (CN) method is widely used for rainfall–runoff modelling in continuous hydrologic simulation models. A sound continuous soil moisture accounting procedure is necessary for models using the CN method. For shallow soils and soils with low storage, the existing methods have limitations in their ability to reproduce the observed runoff. Therefore, a simple one‐parameter model based on the Soil Conservation Society CN procedure is developed for use in continuous hydrologic simulation. The sensitivity of the model parameter to runoff predictions was also analysed. In addition, the behaviour of the procedure developed and the existing continuous soil moisture accounting procedure used in hydrologic models, in combination with Penman–Monteith and Hargreaves evapotranspiration (ET) methods was also analysed. The new CN methodology, its behaviour and the sensitivity of the depletion coefficient (model parameter) were tested in four United States Geological Survey defined eight‐digit watersheds in different water resources regions of the USA using the SWAT model. In addition to easy parameterization for calibration, the one‐parameter model developed performed adequately in predicting runoff. When tested for shallow soils, the parameter is found to be very sensitive to surface runoff and subsurface flow and less sensitive to ET. Copyright © 2007 John Wiley & Sons, Ltd.     

A density‐dependent elastoplastic hydro‐mechanical model for unsaturated compacted soils

This paper presents a three‐dimensional elastoplastic constitutive model for predicting the hydraulic and mechanical behaviour of unsaturated soils. It is based on experimental results obtained from a series of controlled‐suction triaxial tests on unsaturated compacted clay with different initial densities. Hydraulic hysteresis in the water‐retention behaviour is modelled as an elastoplastic process, with the elastic part modelled by a series of scanning curves and the elastoplastic part modelled by the main drying and wetting curves. The effect of void ratio on the water‐retention behaviour is studied using data obtained from controlled‐suction wetting–drying cyclic tests on unsaturated compacted clay with different initial densities. The effect of the degree of saturation on the stress–strain‐strength behaviour and the effect of void ratio on the water‐retention behaviour are considered in the model, as is the effect of suction on the hydraulic and mechanical behaviour. The initial density dependency of the compacted soil behaviour is modelled by experimental relationships between the initial density and the corresponding yield stress and, thereby, between the initial density and the normal compression line. The model is generalized to three‐dimensional stress states by assuming that the shapes of the failure and yield surfaces in the deviatoric stress plane are given by the Matsuoka–Nakai criterion. Model predictions of the stress–strain and water‐retention behaviour are compared with those obtained from triaxial tests with different initial densities under isotropic compression, triaxial compression and triaxial extension, with or without variation in suction. The comparisons indicate that the model accurately predicts the hydraulic and mechanical behaviour of unsaturated compacted soils with different initial densities using the same material constant. Copyright © 2006 John Wiley & Sons, Ltd.